I’ve been steadily gaining muscle with intermittent fasting for over two years now. This page is a comprehensive guide on how to do so.

You will find less citations & explanations here than my usual articles; you can find those scattered throughout the site. I wanted to keep this page as concise as possible.

This page is not meant to convince you of anything. It serves only as a straightforward guide on the fundamentals of gaining lean muscle through intermittent fasting.

Intermittent Fasting Basics

If you’re male, consume all your calories within an 8-hour window and fast for 16 hours daily. Females are better suited to a 10-hour feeding window, fasting for a 14 hours daily.

If you are male, an example schedule would be to break your fast with lunch at 12pm, eating until 8pm.

From 8pm until 12pm the next day (the fasting window) only consume water, zero-calorie tea, and black coffee. No food, sodas, or juices.

You don’t have to be neurotic with the timing, but it’s best to keep it close to the above guidelines. I encourage experimenting with the timing of the fast to find what works best for you: I personally stick to a a 6-hour eating window daily.

#1 – Fasted Training

Start a free-weight training program if you have not already.

For best results, perform your physical training near the end of your fast, on an empty stomach. A study from the European Journal of Applied Physiology found that fasted training resulted in a greater post-workout response than those who trained on a full stomachsource.

However, the effects of pre-workout protein intake have been well-documented. To get the best of both worlds, you can supplement with 10 grams of branched chain amino acid (BCAA) immediately before your workout for optimal muscle growthsource. This is by no means mandatory, but I’m aware some of you are intent on milking out the maximum possible natural growth per month.

If you do end up supplementing with BCAA, choose a powdered form like the one I linked instead of tablets (which are more expensive/more hassle). It’s going to taste terrible, and the recommended dose is two teaspoons. What I do is take the teaspoon, drop it near the back of my tongue, and quickly wash it down with water.

#2 – Calorie Intake

First, go to this calorie calculator. If your main source of exercise is going to the gym, select Somewhat Active. Only select Active/Very Active if you train daily for athletic events (swimming, track, etc), or work a manual labor job. I routinely see people overestimating the amount of calories that they need to consume.

Use the number the calculator reports as your starting estimate for your daily caloric maintenance level.

Weigh yourself every morning, after you go to the bathroom, but before eating/drinking anything (ensuring the most accurate result). Track your weight in an Excel/Google Docs spreadsheet.

Smartphone apps such as MyFitnessPal make it easy to track both calorie & macronutrient intake with little hassle. I’ve been using this food scale for two years now to make estimating volumes easier and more accurate. When weighing meat, weigh it raw, rather than after you cook it.

Option #1) Lose fat slowly, Build muscle slowly: Recomposition

Often simply called a “recomp”, this option maintains the same weight while slowly building muscle and losing fat. No weekly caloric surplus or deficit. Only intermittent fasting, macro-nutrient cycling, and caloric cycling.

This allows “skinnyfat” beginners wary of gaining additional body-fat to get started with weightlifting. Beginners can build muscle easily while losing their bodyfat, and when their progress eventually slows they can rotate between bulking and cutting cycles.

The downside to recomposition is that you make much slower progress. How far can you really progress when you stay 135 pounds for months on end? It is for this reason that I do not recommend recomps to any trainer beyond a beginner level.

If you choose recomposition, your weekly calorie intake should match the maintenance level the calculator above gave you, and you want your weight to stay the same (adjusting your calories every two weeks to try to “zero in” on maintaining the same weight).

However, for daily intake, you want higher calories on workout days, lower calories on rest days. This is where the “calorie cycling” comes in. It’s up to you on how to divide the calories up, but here’s an example with a 2000 calorie maintenance.

Monday (Workout): 2000 + 200 = 2200 calories

Tuesday (Workout): 2000 + 200 = 2200 calories

Wednesday (Rest): 2000 – 266 = 1734 calories

Thursday (Workout): 2000 + 200 = 2200 calories

Friday (Workout): 2000 + 200 = 2200 calories

Saturday (Rest): 2000 – 266 = 1734 calories

Sunday (Rest): 2000 – 266 = 1734 calories

AVERAGE DAILY CALORIES = 2000 calories

Option #2) Lose fat quickly, Retain Muscle: Cut

Refer to this picture to roughly determine your bodyfat percentage. If you lose weight at the rate listed below, you will preserve your strength during the cut, and perhaps even slowly gain some. Women & shorter males should aim for a slightly slower weekly loss than the figures listed.

>20% bodyfat – 2 pounds weight loss per week

12-19% bodyfat – 1 pound of weight loss per week

<12% bodyfat – 0.5-0.75 pounds of weight loss (lower end will be trickier and will have slower progress, but will retain the most lean tissue)

For example, let’s say that you are 15% bodyfat, and aiming for 1 pound of fat loss per week. One pound of weight loss is roughly equal to a 3500 calorie deficit, so aim for a 3500 weekly deficit to lose roughly one pound of fat per week. Alternatively, a 1750 calorie could be used to lose a half pound of fat per week.

Eat at maintenance calories for your workout days, and divide the rest of the needed deficit between your rest days. An example diet with a 2300 calorie maintenance, aiming for a weekly deficit of 3000 calories:

Monday (Workout): 2300 calories [0]

Tuesday (Workout): 2300 calories [0]

Wednesday (Rest): 1300 calories [-1000]

Thursday (Workout): 2300 calories [0]

Friday (Workout): 2300 calories [0]

Saturday (Rest): 1300 calories [-1000]

Sunday (Rest): 1300 calories [-1000]

Adjust your calorie intake if your weight loss doesn’t reflect your expectations. For example, if your weight loss plateaus for two weeks in a row, you could subtract 100 calories every day from your intake.

If you’re exceedingly hungry during your cut, you may find advice from this page useful.

Option #3) Build Muscle, Minimal Fat Gain: Slow Bulk

Another mistake that I commonly see is for trainers to bulk too quickly, gaining fat and muscle in equal portions. They consume at a needlessly high caloric surplus, gain too much fat during their bulks, waste time burning it off later, and are often disappointed with spending so much time at higher bodyfat percentages.

What rate of weight gain should you be aiming for? The answer depends on how long you’ve been training.

A trainee with less than 2 years experience can expect to naturally build 2 pounds of lean muscle per monthsource. That means the most you should aim to gain is 2 pounds of weight per month. Some of this may be fat but most will be muscle if you follow a half-decent program.

One pound of weight gain is roughly equal to a 3500 calorie surplus. Since we are aiming for a half pound of weight gain per week, our weekly surplus is going to equal +1750 calories.

Note: If you have more than 2+ years of proper training, you will not be able to put on muscle as quickly as a new lifter. For you, I would recommend slower gains: a 1000-1250 caloric surplus per week. You will have to track your intake carefully.

As for daily intake, eat at maintenance calories on your rest days. Divide your caloric surplus evenly among your workout days. For example, if you work out four days a week with a 1750 calories surplus: 1750/4 = 437 calorie surplus every workout day. If the calculator above gave you 2300 calories as your maintenance levels, here’s an example of what your week may look like:

Monday (Workout): 2737 calories [+473]

Tuesday (Workout): 2737 calories [+473]

Wednesday (Rest): 2300 calories [0]

Thursday (Workout): 2737 calories [+473]

Friday (Workout): 2737 calories [+473]

Saturday (Rest): 2300 calories [0]

Sunday (Rest): 2300 calories [0]

Adjust your calorie intake if your weight change doesn’t reflect your expectations. If your spreadsheet shows that you are gaining weight at a rate greater than what you were aiming for (for two weeks straight) scale your calories back. If your weight gain has stalled for two weeks straight, consider increasing your calorie intake.

Between Bulk & Cut Cycles:

When you’re finishing a bulk and are ready to cut, or are finishing a cut and are ready to bulk, spend two weeks in the “recomposition” stage before switching — with weekly caloric intake equal to your maintenance levels. This gives your metabolism some time to adapt to the new level of caloric intake.

Step #3: Macronutrient Cycling

Now that calorie cycling is out of the way, it’s high time to address macronutrient cycling. There are three macros: fat, protein, and carbohydrates.

Cycling macros allows you to maximize the muscle-building benefits of carbohydrates on your workout days, and the hormone-production benefits of fat intake on your rest days.

The exact percentages each day are not important. Your number one priority is to hit your protein intake goal, then fill in the remaining calories with fat/carbohydrates depending on if it’s a workout day or a rest day.